Rf and if automatic gain control circuitry with extended range if control

Claim 2

In a a wave signal receiver for signals of varying strength having an RF stage with variable gain and an IF stage with variable gain, an automatic gain control circuit comprising: first circuit means responsive to the received signal strength for developing a first automatic gain control signal; means for coupling said first automatic gain control signal to one of said variable gain stages; second circuit means for developing a second automatic gain control signal having a substantially constant magnitude for received signal strengths less than a first prescribed level and having a magnitude proportional to said received signal strength for received signal strengths equal to or greater than said first prescribed level; means for coupling said second gain control signal to the other of said variable gain stages; and third circuit means operative at a second prescribed received signal level greater than said first prescribed level, for coupling said second automatic gain control signal to said one variable gain stage to supplement said first automatic gain control signal applied to said one variable gain stage.

Claim 3

The automatic gain control circuit of claim 1 wherein said one variable gain stage comprises said IF stage and said other variable gain stage comprises said RF stage.

Claim 4

The apparatus of claim 2 wherein: said first circuit means includes an amplifier for producing said first automatic gain control signal in proportion to said received signal strength; and said second circuit means includes an amplifier responsive to said received signal attaining a first prescribed level to produce said second automatic gain control signal in proportion to said received signal strength.

Claim 5

The automatic gain control circuit of claim 2 wherein the gain control signals applied to the RF and IF stages are DC voltages.

Claim 6

The automatic gain control circuit of claim 3 wherein said second automatic gain control signal increases responsive to increased signal strength at a greater rate than said first automatic gain control signal so that above a predetermined received signal level, less than said second prescribed received signal level, said second automatic gain control signal exceeds said first automatic gain control signal by increasing amounts, and wherein said third circuit means responds to said second automatic gain control signal exceeding said first automatic gain control signal by a prescribed amount to supplement said first automatic gain control signal with said second automatic gain control signal.

Claim 7

The automatic gain control circuit of claim 5 wherein said third circuit means includes a diode having a predetermined breakdown voltage.

Claim 8

In a radio wave receiver for signals of varying strength having an RF stage with variable gain and an IF stage with variable gain, an automatic gain control circuit comprising: first means for developing a signal representative of the received signal strength; a first load connected to the IF stage and across which an IF gain control signal is developed; a second load connected to the RF stage and across which an RF gain control signal is developed; second means responsive to the representative signal for developing a gain control signal across the first load which is dependent upon received signal strength; third means associated with the second means and responsive to the IF gain control signal exceeding a prescribed level for deveLoping a gain control signal across the second load which is dependent upon received signal strength; and means connected between the loads for causing the RF gain control signal to develop a supplementary control signal across the first load when the control signal developed across the second load exceeds the control signal developed across the first load by a predetermined amount.

Claim 9

In a radio wave receiver for signals of varying strength having an RF stage with variable gain and an IF stage with variable gain, an automatic gain control circuit comprising: first means for developing a signal representative of the received signal strength; a first load connected to the IF stage and across which an IF gain control signal is developed; a second load connected to the RF stage and across which an RF gain control signal is developed; second means responsive to the representative signal for developing a gain control signal across the first load which is dependent upon received signal strength; third means associated with the second means and responsive to the IF gain control signal exceeding a prescribed level for deveLoping a gain control signal across the second load which is dependent upon received signal strength; and means connected between the loads for causing the RF gain control signal to develop a supplementary control signal across the first load when the control signal developed across the second load exceeds the control signal developed across the first load by a predetermined amount.

Claim 10

The automatic gain control circuit of claim 7 wherein the loads are resistors across which DC voltages are developed and the connecting means is in the form of a diode which allows current to flow from the second load through the first load when the difference in voltages developed across the loads exceeds the diode breakdown voltage.